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national aeronautics and space administration 


Arecibo S-Band Radar Program 


National Astronomy and Ionosphere Center 
Space Sciences Building 
Cornell University 

Ithaca.. N.Y. 14853 


Donald B. Campbell 

DESCRIPTION la. Brief statement on strategy of investigation; b. Prog ress and accomplishments of prior year; c. What will be accomplished 
this year, as well as how and why; and d. Summary bibliography) 

a) General Objectives : The high powered 12.6cm wavelength radar on the 1000-ft Arecibo 

reflector is utilized for a number of solar system studies. Chief among these are: 1) 
Surface reflectivity mapping of Venus, Mercury and the Moon. Resolutions achievable on 
Venus are less than 1.5km over some areas, for Mercury about 30km and for the Moon 200m 
at present. 2) High time resolution ranging measurements to the surfaces of the 
terrestrial planets. These measurements are used to obtain profiles and scattering 
[parameters in the equatorial region. They can also be used to test relativistic and 
| gravitational theories by monitoring the rate of advance of the perihelion of the orbit 
'of Mercury and placing limits on the stability of the gravitational "constant". 3) 
(Measurements of the orbital parameters, figure, spin vector and surface properties of 
| asteroids and comets. 4) Observations of the Galilean Satellites of Jupiter and the 
satellites of Mars, Phobos and Diemos . 

,b) Past Twelve Months : The Galilean Satellites of Jupiter were re-observed with the 

12.6cm radar for the first time since 1981. Much more accurate measurements of the 
scattering properties of the three icy satellites were obtained that generally con- I 
firmed previous observations. Unambiguous measurements of the cross section and ' 
icircular polarizations ratio of Io were also obtained for the first time. The radar j 
(scattering properties of four mainbelt asteroids and one near-earth asteroid were 
studied and the turbulence spectrum of the solar wind within 20 solar radii of the Sun 
,was measured by examining propagation effects on echoes reflected from Venus when it . 
was close to superior conjunction. Late May saw a commencement of a new set of mapping : 
observations of Venus. Papers covering observations of Comets IRAS-Araki-Alcock and [ 
jHalley, measurements of turbulence in the solar wind and studies of the surface of 
Venus were submitted for publication. 

|c) Next Twelve Months : A heavier than normal observing schedule is planned for the next 
eight months .Mapping observations of Venus will continue until early July, Mars’ 
[observations aimed at delineating areas of high surface roughness will commence in 
August and an attempt will be made to detect the satellites of Mars, Phobos and Diemos, 
jin September .Approximately twenty observing sessions will be devoted to measurements of 
Ithe scattering properties of the Galilean Satellites at both 70cm and 12.6cm wave- j 
(Lengths .Detailed topographic measurements of Aphrodite Terra on Venus will be made in . 
(Late summer and fall aimed at attempting to verify the suggestion that this region | 

pontains numerous cross strike discontinuities and the program of high resolution j 

(<100m) imaging of the moon will recommence in early 1989. A number of asteroids will be 

observed including the small earth approaching objects. 433 Eros. 1685 Toro and 1980 PA. i 




d. Publications 

Head, J.W., Crumpler, L.S., Bindschadler , D.L. , Stofan, E.R. , 

VorderBruegge , R.W. and Campbell, D.B., Venus Geology and Geophysics: A 

Review of Some Recent Studies, Astron. Vestnik, 21, 99, 1987. 

Basilevsky, A.T. , Ivanov, B.A. , Burba, G.A. , Chernaya, I.M., Kryuchkov, 
V.P., Nikovaeva, O.V. , Campbell, D.B. and Ronca, L.B. , Impact Craters of 
Venus: A Continuation of the Analysis of Data from the Venera 15 and 16 

Spacecraft, J. Geophys . Res., 92, 12, 869, 1987. 

Harmon, J.K. and Campbell, D.B. , Radar Observations of Mercury, in press, 
Proceedings of the Conference on Mercury, Tucson, Arizona, 1986. 

Crumpler , L.S., Head, J.W. and Harmon, J.K., Regional Linear Cross-Strike 
Discontinuities in Western Aphrodite Terra, Venus, Geophys. Res. Lett., 14, 
607, 1987. 

Coles, W.A. and Harmon, J.K., Radar Propagation Observations of the Solar 
Wind Near the Sun, submitted to the Astrophys. J. 

Harmon, J.K., Campbell, D.B., Hine, A. A. , Shapiro, I. I. and Marsden, 

B.G., Radar Observations of Comet IRAS-Araki-Alcock, submitted to the 
Astrophys. J. 

Campbell, D.B., Harmon, J.K. and Shapiro, 1. 1., Radar Detection of Comet 
Halley, submitted to the Astrophys. J. 

Stofan, E.R. , Head, J.W., Campbell, D.B., Zisk, S.H., Bogomolov, 

A.F., Rzhiga, O.N. , Basilevsky, A.T. and Armand, N. , Geology of a Rift Zone 
on Venus: Beta Regio and Devana Chasma, submitted to the GSA Bulletin.